Unlicensed Mobile Access (UMA) technology provides access to Global System for Mobile Communications (GSM) services and General Packet Radio Service (GPRS) mobile services over unlicensed spectrum technologies, including Bluetooth and 802.11. In order to promote the widespread adoption of UMA technology, a number of leading companies within the wireless industry have jointly developed a set of open specifications. In addition to developing and maintaining the initial specifications, the participating companies are actively working with the 3GPP standards organization to use the specifications as the basis for the development of a formal standard.
However, UMA has several deficiencies. For example, UMA is dependent on legacy GSM protocols, and suffers from lack of support for the Session Initiation Protocol (SIP), which enables call control for Voice over IP (VoIP) and IP Multimedia Subsystem (IMS) networks.